Comparison of Pressure Support and Pressure Control Ventilation in Chronic Respiratory Failure

Inclusion Criteria: * Patients with chest wall deformity, neuromuscular disease or obesity hypoventilation syndrome with an FEV1/FVC ratio of \>70% and VC \<50% predicted or patients with COPD with a FEV1/FVC ratio of \<70% an FEV1 \<50% predicted * Stable * pH \>7.35 * ESS \<18 * Symptomatically stable with clinical resolution of intercurrent infection: normal C reactive protein, white cell count and afebrile * Daytime symptoms compatible with nocturnal hypoventilation i.e. poor sleep, morning headache, daytime somnolence, shortness of breath * Arterial carbon dioxide partial pressure (PaCO2) \> 6.0kPa during day with evidence of nocturnal hypoventilation (TcCO2 \>7.5KPa or a rise in TcCO2 of \>1 KPa) * No prior domiciliary ventilation use * Patients with COPD must be established on optimal medical treatment prior to enrolment Exclusion Criteria: * Psychological, social or geographical situation that would impair compliance with the schedule * Patients who have underlying malignancy or severe cardiac dysfunction (ejection fraction \<40%) * Complex OSA